<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>js</title>
    <script src="../js/jquery-3.3.1.min.js"></script>
</head>
<body>

<ul>
    <li id="yi">1</li>
    <li class="er">2</li>
    <li>3</li>
    <li>4</li>
    <li>5</li>
    <li>6</li>

</ul>





<script src="../js/re.js"></script>
</body>
</html>